Dark territory is a term used in the North American railroad industry to describe a section of running track not controlled by signals. Train movements in dark territory were previously handled by timetable and train order operation, but since the widespread adoption of two way radio communications these have been replaced by track warrants and direct traffic control, with train dispatchers managing train movements directly. Today most dark territory consists of lightly used secondary branch lines and industrial tracks with speeds ranging between 25 miles per hour (40 km/h) and 40 miles per hour (64 km/h); however, there do exist a small minority of main lines that fall into the category.
In the UK and Australia the term applies to rail track where the signalling system does not pass the signal indications nor track occupancy back to a signal box. As such the position of trains is not visible to signallers, and so the track is "dark".
The primary safety concerns with dark territory stems from the lack of any form of direct or indirect train detection along the route. Train detection systems such as track circuits not only alert other trains to the presence of a potential hazard, but can also alert dispatchers or other monitoring systems to the same. Dark territory also lacks the ability to control or lock switches onto the main track, detect misaligned switches, broken rails or runaway rail cars. In most cases these drawbacks are mitigated by the light traffic and low speed of the trains in dark territory, but a runaway train (such as the crude oil unit train in 2013's Lac-Mégantic derailment) will not respect limits on speed and is not detectable by rail traffic controllers on a line with no signals or track circuits.
The total reliance on manual procedures to ensure safety has occasionally resulted in train wrecks, some with fatalities, due to either miscommunication or oversight on the part of operating personnel. In 1948 the Interstate Commerce Commission set a nationwide speed limit of 60 miles per hour (97 km/h) for trains not protected by some kind of block system (including manual block and track warrants) and in 2012 this was expanded to include all lines considered dark territory. Since 1991 the National Transportation Safety Board (NTSB) had recommended that railroads be required to install new forms of signaling technology, such as positive train control (PTC), that can stop trains from exceeding their procedural authorities and warn them of improperly lined switches. The Rail Safety Improvement Act of 2008 and subsequent amendments requiring installation of PTC technology on parts of the U.S. rail network by December 31, 2018, may eliminate many sections of currently dark territory.
On specific railroads
The Gateway Subdivision of BNSF Railway, in California and Oregon, is unsignalled and operates with track warrant control (TWC), as is the El Paso Subdivision located in Southern New Mexico. The Phoenix Subdivision is an approximately 200-mile-long mainline subdivision running north/south in Arizona operating under verbal track warrant.
Dakota, Minnesota and Eastern Railroad
The Waseca Subdivision of the Dakota, Minnesota and Eastern Railroad, a 103-mile (166 km) freight line in Minnesota, is not signalled and uses TWC. Several other portions of the railroad converted to signalled operation in 2008.
Iowa, Chicago and Eastern Railroad
- General Code of Operating Rules
- Glossary of rail transport terms
- North American railway signaling
- Runaway train
- U.S. National Transportation Safety Board (June 13, 2006). "Failure to Adhere to Track Warrant Control Rules Caused Collision of Two BNSF Trains in Gunter, Texas, NTSB Says".
- "Rail transportation safety investigation R13D0054 (Lac-Mégantic derailment of 6 July 2013)". Transportation Safety Board of Canada. 6 Jul 2013.
- "Original 'Most Wanted' List of Transportation Safety Improvements, as adopted September 1990". ntsb.gov. 1991. Archived from the original on 25 March 2011. Note: The original NTSB list used the term "Positive Train Separation," which was revised to "Positive Train Control Systems" in 1991.
- "Obama signs short-term transportation bill". Washington Post. 2015-10-29. Archived from the original on 2019-03-08.
- "Accident Investigation Report HQ-2005-03: Burlington Northern Santa Fe (BNSF), Bieber, California, January 8, 2005" (PDF). U.S. Federal Railroad Administration (FRA). 2005. Archived from the original (PDF) on March 20, 2012.
- "Freight Rail Supply and Demand; Draft Technical Memorandum". Minnesota Comprehensive Statewide Freight and Passenger Rail Plan (PDF). Minnesota Department of Transportation. 2009. pp. 3–12.
- Stagl, Jeff (October 2008). "Suppliers tweak train-control systems to help railroads avoid dark territory accidents". Progressive Railroading. Milwaukee, WI: Trade Press Media Group. Archived from the original on 2010-12-18.
- "Railroad Switch Safety Demonstration Begins Testing". FRA. November 14, 2005. Archived from the original on 2009-05-09.